The descriptive terminology employed herein is that generally used and recognized by highway authorities throughout North America. A "highway" includes any type of load bearing surface, prepared or unprepared. A "vehicle" is any type of mobile transport equipment intended for operation on a highway. An "axle" includes, wheels, tires, brakes and such other equipment as required by applicable regulations. A "suspension" is the device by which the axles are attached, or mounted to the vehicle, or vehicle sub frame.
A "resilient suspension" is one intended to allow and provide for some predetermined degree of deflection between the vehicle and the highway, beyond that afforded by pneumatic tires alone.
An "equalizing resilient suspension" is one that by mechanical, pneumatic, hydraulic, or other interconnecting means, is intended to equalize loads between two or more adjacent axles, which might otherwise be unequally loaded to the point of overloading any individual axle--such unequal loading as would be induced by the vehicle passing over uneven terrain, or the vehicle assuming an attitude in the direction of travel other than parallel with the highway.
The essence of a resilient suspension is that vertical deflection of an axle caused by increasing loading, generates an increasing resistance to deflection in the suspension, proportional to the deflection, until the point is reached at which the axle has attained the design limit of travel, and it is then said to have "bottomed out".
The prime objective of an equalizing resilient suspension is to distribute unequal loading of any axle or axles to all axles in a group, and thus avoid premature "bottoming out" until all axles in the group have attained their proportional share of the group loading bottoming out force.
There are many types of resilient equalizing suspension commercially available on the North American market.
All such suspensions are designed on the basis that a straight line projected through the horizontal longitudinal centre line of the axles is parallel to the base structure of the suspension, and this geometry is a fixed condition in the attachment to the vehicle. It follows that when a travelling vehicle encounters terrain that alters the parallel fore & aft relationship between the "highway" bearing surface and the vehicle, the geometry of the suspension is altered accordingly.
The effect of the altered geometry is that the fore or aft axle of the group will "bottom out" at some group loading less than the design intention, as dictated by the degree of deviation from the design parallelism.
Another problem encountered in the prior art is the presence of cantilever bending stresses in the intermediate suspension of a "B" train multiple vehicle configuration. In the "B" train configuration, the suspension frame of a forward vehicle is extended rearwardly to allow the front of the following vehicle to be carried on the common suspension. The rearwardly extending structure, when rigidly attached to the forward vehicle, is cantilevered and is thus subject to significant cycling bending stresses. In addition, weight distribution considerations, and space limitations, invariably locate the king pin weight bearing point of the following vehicle behind the centre of reaction of the common suspension, and thus generate a cantilever moment downward ward on the common suspension and equally upwardly on the lead king pin in the proportion of the respective moment arms. This moment significantly increases the structural bending stresses.
The aim of this invention is to ameliorate the difficulties of the prior art.